• synonyms


[sil-ee-uh m]
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  1. singular of cilia.
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Origin of cilium

From Latin


plural noun, singular cil·i·um [sil-ee-uh m] /ˈsɪl i əm/.
  1. Biology. minute hairlike organelles, identical in structure to flagella, that line the surfaces of certain cells and beat in rhythmic waves, providing locomotion to ciliate protozoans and moving liquids along internal epithelial tissue in animals.
  2. Anatomy. the eyelashes.
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Origin of cilia

1705–15; New Latin, plural of cilium eyelash, Latin: upper eyelid, perhaps a back formation from supercilium eyebrow; see supercilium
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for cilium

Historical Examples

  • Each consists of a very slender curved filament, with a still finer filament, or cilium, arising from it on each side.

    An Elementary Text-book of the Microscope

    John William Griffith

British Dictionary definitions for cilium


noun plural cilia (ˈsɪlɪə)
  1. any of the short thread-like projections on the surface of a cell, organism, etc, whose rhythmic beating causes movement of the organism or of the surrounding fluid
  2. the technical name for eyelash
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Word Origin

C18: New Latin, from Latin: (lower) eyelid, eyelash


  1. the plural of cilium
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Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for cilium



1715, from Latin cilia, plural of cilium "eyelid, eyelash," perhaps related to celare "to cover, hide," from PIE root *kel- "to conceal" (see cell), but words for this part of the face can be tricky (see brow). It sometimes is pluralized in English, which is an error. Related: Ciliated; ciliary; ciliate.

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Online Etymology Dictionary, © 2010 Douglas Harper

cilium in Medicine


n. pl. cil•i•a (-ē-ə)
  1. eyelash
  2. A microscopic hairlike process extending from the surface of a cell or unicellular organism, capable of rhythmical motion, and acting with other such structures to cause the movement of the cell or of the surrounding medium.

cilium in Science